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Researchers Submit Patent Application, "Ac/Dc Converter and Method of Correcting Power Factor", for Approval

June 25, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors PAN, Ching-Tsai (Hsinchu, TW); CHEN, Po-Yen (Taipei, TW); HUNG, Ta-Sheng (TAICHUNG, TW), filed on December 4, 2013, was made available online on June 12, 2014.

The patent's assignee is Hep Tech Co., Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates generally to a converter, and more particularly to an AC/DC converter and method of correcting power factor.

"Typically, an AC/DC converter is used to convert an alternate current (AC) into a direct current (DC). FIG. 1 shows a conventional AC/DC converter, which includes a rectifier circuit 300 and an output capacitor C. The rectifier circuit 300 converts an alternate current (AC) of an AC power supply into a direct circuit (DC), and the output capacitor C bridges over the outputs of the rectifier circuit 10 and are connected to a loading 400 in parallel. While the AC/DC converter is working, the phases of the input voltage and the input current of the AC are different, which leads to low power factor and poor total harmonic distortion. In addition, the output capacitor C is charged only when the direct current has higher voltage than the output capacitor C, hence the charging time of the output capacitor C is shortened. As a result, the conduction time of diodes in the rectifier circuit 300 is also shortened, which increases the peak value of the conduction current, distorts the waveform of the input current, and lowers the power factor. Low power factor not only wastes energy, but also poses unnecessary burdens for the power supply systems of the power company. Therefore, the AC/DC converter with power factor correction circuit is emerged.

"Typically, a conventional power factor correction circuit for AC/DC converters has two types, which are active type and passive type. Active power factor correction circuits control the input current with active switch components, and this type of power factor correction circuits has several advantages, such as the power factor could excess 0.99, and the total harmonic distortion could be less than 10%. And moreover, active power factor correction circuit is compatible with wider range of input voltage, generates stable output voltage, and it's unaffected by the variation of output power. However, active power factor correction circuit has several main drawbacks too, such as higher cost due to additional active switch components required, high electromagnetic noises, and low durability. The industry is eager to overcome these drawbacks. Besides, in order to reduce the ripple of the output voltage of the loading 400, the aforementioned output capacitor C has to adopt a high capacity electrolytic capacitor, but the electrolytic capacitor is easy to leak out the contained electrolyte due to being heated for a long period of time, which shortens life of circuit."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "In view of the above, the primary objective of the present invention is to provide an AC/DC converter and a method of correcting power factor, which effectively increases the power factor, and suppresses voltage ripples provided to a loading.

"The present invention provides an AC/DC converter for converting an alternate current (AC) of a power supply into a direct current (DC), and the DC is transmitted to a loading, which includes a rectifier circuit and an active power factor correction circuit, wherein the rectifier circuit is electrically connected to the power supply to convert the AC into the DC, which has a positive output and a negative output for outputting the DC; the active power factor correction circuit electrically connects the rectifier circuit to the loading, which is used to suppress voltage ripples provided to the loading, and includes a first diode, a second diode, a third diode, a first inductor, a second inductor, a first capacitor, a switch, a fourth diode, a third inductor, a second capacitor, and a third capacitor, wherein the first diode has an anode and a cathode, wherein the cathode of the first diode is connected to the positive output of the rectifier circuit; the second diode has an anode and a cathode, wherein the anode of the second diode is connected to the negative output of the rectifier circuit; the third diode has an anode and a cathode, wherein the anode of the third diode is connected to the anode of the first diode; the first inductor has two ends, one of which is connected to both the cathode of the first diode and the positive output of the rectifier circuit; the second inductor has an end connected to the cathode of the second diode and an opposite end connected to the anode of the first diode and the anode of the third diode; the first capacitor has an end connected to the first inductor and an opposite end connected to the second inductor, the anode of the second diode and the anode of the third diode; the switch has an end connected to both the first inductor and the first capacitor and an opposite end connected to both the negative output of the rectifier circuit and the anode of the second diode; the fourth diode has an anode and a cathode, wherein the anode of the fourth diode is connected to both the cathode of the second diode and the second inductor, and the cathode thereof is connected to the cathode of the third diode; the third inductor has an end connected to both the cathode of the third diode and the cathode of the fourth diode; the second capacitor has an end connected to both the cathode of the third diode and the cathode of the fourth diode and an opposite end connected to the third inductor; the third capacitor has an end connected to both the third inductor and the second capacitor and an opposite end connected to the cathode of the second diode, the second inductor and the anode of the fourth diode, wherein the third capacitor is connected to the loading in parallel.

"According to the aforementioned concepts, the present invention further provides a method of correcting power factor with an active power factor correction circuit, wherein the active power factor correction circuit includes a first diode, a second diode, a third diode, a first inductor, a second inductor, a first capacitor, a switch, a fourth diode, a third inductor, a second capacitor, and a third capacitor, wherein the first diode has an anode and a cathode, wherein the cathode of the first diode is connected to the positive output of the rectifier circuit; the second diode has an anode and a cathode, wherein the anode of the second diode is connected to the negative output of the rectifier circuit; the third diode has an anode and a cathode, wherein the anode of the third diode is connected to the anode of the first diode; the first inductor has two ends, one of which is connected to both the cathode of the first diode and the positive output of the rectifier circuit; the second inductor has an end connected to the cathode of the second diode and an opposite end connected to the anode of the first diode and the anode of the third diode; the first capacitor has an end connected to the first inductor and an opposite end connected to the second inductor, the anode of the second diode and the anode of the third diode; the switch has an end connected to both the first inductor and the first capacitor and an opposite end connected to both the negative output of the rectifier circuit and the anode of the second diode; the fourth diode has an anode and a cathode, wherein the anode of the fourth diode is connected to both the cathode of the second diode and the second inductor, and the cathode thereof is connected to the cathode of the third diode; the third inductor has an end connected to both the cathode of the third diode and the cathode of the fourth diode; the second capacitor has an end connected to both the cathode of the third diode and the cathode of the fourth diode and an opposite end connected to the third inductor; the third capacitor has an end connected to both the third inductor and the second capacitor and an opposite end connected to the cathode of the second diode, the second inductor and the anode of the fourth diode, wherein the third capacitor is connected to the loading in parallel; the method includes the steps of:

"A. Conduct the switch to let the DC power supply charge the first inductor with a DC, the first capacitor charge the second inductor to make the second inductor have a stored energy, and the third inductor, the second inductor and the third inductor provide energy to the loading;

"B. Cut off the switch and conduct the first diode to let the first inductor provide energy to the first capacitor, and keep transmitting the stored energy of the second inductor to the third capacitor;

"C. Conduct the fourth diode to let the second capacitor and the third inductor provide energy to the third capacitor to provide energy into the loading;

"D. Keep providing energy from the second capacitor and the third inductor to the third capacitor to provide energy into the loading as the first diode is cut off after the first inductor finishing providing energy to the first capacitor.

"With such design, it may effectively increase the power factor of the AC/DC converter, and suppress voltage ripples provided to the loading.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

"The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which

"FIG. 1 is a circuit diagram of the conventional AC/DC converter;

"FIG. 2 is a circuit diagram of a preferred embodiment of the present invention;

"FIG. 3 to FIG. 6 are the circuit diagrams of the preferred embodiment of the present invention, showing how the AC/DC converter works in different steps;

"FIG. 7 is an oscillogram of the output voltage and the output current."

For additional information on this patent application, see: PAN, Ching-Tsai; CHEN, Po-Yen; HUNG, Ta-Sheng. Ac/Dc Converter and Method of Correcting Power Factor. Filed December 4, 2013 and posted June 12, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4166&p=84&f=G&l=50&d=PG01&S1=20140605.PD.&OS=PD/20140605&RS=PD/20140605

Keywords for this news article include: Electronics, Hep Tech Co. Ltd, Electrolytic Capacitor.

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Source: Electronics Newsweekly


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